A semiconductor device as a sensor includes a case and a cover, which is disclosed in U.S. Pat. No. 6,906,412 corresponding to JP-A-2004-3886. The case accommodates a semiconductor chip, and the cover seals an opening of the case. Specifically, the sensor includes the semiconductor sensor chip, a package as the case and a lid as the cover. The package has a rectangular box shape, and the lid has a rectangular plate shape. The sensor chip is mounted on an inner bottom of the package. A terminal base is formed on the inner bottom of the package, and a bonding pad is formed on the terminal base. The sensor chip is connected to the bonding pad through a bonding wire. The opening of the package is covered and sealed with the lid.
The above sensor is integrally molded together with other electric elements for providing a circuit for the sensor. However, since the lid has the rectangular plate shape, the lid may be deformed toward the package side by pressure in a molding process. When the lid is made of metal, the lid may contact the semiconductor chip or the bonding wire so that the deformation causes to short-circuit the chip.
When the lid is made of material other than metal, for example, when the lid is made of resin, the deformation may cause to generate stress in the bonding wire or the semiconductor chip. When the thickness of the lid becomes larger, the manufacturing cost of the sensor increases. Further, in case of thick lid, when the lid is fixed by a welding method, the welding becomes difficult because the thick lid radiates heat largely.
Thus, it is required for the sensor to improve pressure resistance of the lid.